This was the poster Luc Besson created, as a blueprint, with the intention of shooting "Mathilda," a sequel to 1994's "Leon: The Professional."

This was the poster Luc Besson created as a blueprint with the intention of shooting a sequel to "Leon: The Professional." 

Besson’s "Leon" has gained such a fervent following ever since the rather mixed reaction it got upon its release back in 1994. It was the emergence of Natalie Portman and Luc Besson in American cinema. Ever since then there have been countless rumors going around about a possible follow-up that would be centered around Portman’s character, Mathilda, and her life after the events of the first movie. A decade ago there even was a rumor about Portman having already signed on for the sequel. That was proven to be false by her reps.  However, Portman has always stated she would be open to the idea of making sequel. 

Here is Portman in her own words talking about the possibility of a sequel to IndieWire

Ten years ago we decided to make ‘Mathilda,’ which was the ‘Professional’ sequel, but we couldn’t do it because of the evolution of a lot of things – about Natalie [Portman], about [estranged distributor] Gaumont. Luc tried to do this movie again and again—he proposed it to me 12 years ago. But when we decided to change the script and to make another movie with a revenge story like ‘Mathilda,’ he had to give up everything about Mathilda. When you write a script you always think about what your heart is asking. If Mathilda was there, she should have done this or that. He had to forget everything, because it’s a new story.

During promotional rounds for his movie "Colombiana," director Olivier Megaton -yeah that's really his last name- stated that he actually intended for the script to be the follow-up to "Leon," called "Mathilda." He claims that he had been working on the script with Besson for 12 years, but there were just too many problems securing Portman to star in the vehicle and the original distributor was making their lives dificult in allowing the rights to be used. Besson ended up producing "Colombiana." That turned out to be a mediocre film, there were no scenes that really grabbed me and I have officially disregarded it as having anything to do with "Leon" or "Mathilda." 

With an 8.6 rating out of more than 745,000  votes on IMDB, "Leon: The Professional" is ranked 27th on the IMDB all-time top 250 list. A vast difference from the original, mixed reviews the film got back in 1994.

The original script of "Leon" actually had her committing suicide at the end of the movie. Leon is killed and Matilda is the one who kills all of them (Gary Oldman and the police) because she has grenades strapped to her jacket. 

Also, they have sex.

Would have made for one hell of an awkward moment. Good thing they got rid of that scene. Even though it is insinuated throughout the film how much of a flirt Mathilda is towards Leon, this is the kind of risky scene that could easily kill a film's vibe or momentum.